Composite glass-metal article



Oct, 29, 1940. v. H. FRAENCKEL s y 2,219,574

ouPosITE GLASS-METAL Annaba original Filed June 1,' 193e s snees-sheez 2 .5- /7 ,6 i. Tj

0d' 29 v1940. v. H. FRAENCKEL 2,219,574

" w'uPosITE GLASS-METAL Amicus original Filed June l, 1936 5 Sheets-Sheet 3 TS1-Ef INVENTOR ATTORNEY Patented Oct. 29,

UNITED "STATES 2,219,574 l COMPOSITE GLASS-METAL ARTICLE Victor H. Fraenckel, Wyndmoor, Pa., assignor to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Original application June 1, 1936, Serial No. 82,742. Divided and this application March 29,

1937, Serial No. 133,547

(Cl. Z50-141) 3 Claims.

This invention relates to composite glass-metal articles and more particularly to such devices as electron discharge tubes, cathode ray tubes,

electric lamps and the like.

A principal object of the invention is to provide an improved method of forming a vacuumtight bond between a metal member and a glass or other vitreous-like body.

' Another object is toprovide an improved headl0 er or base for electron discharge tubes, vas well as an improved method of forming such a header or base.

Another object is to provide an improved window or screen for such devices as cathode ray tubes and the like.

A further object is to provide an improved base or header for a radio tube, the header consisting of a glass body sealed in a vacuum-tight manner to a metal frame or flange.

A still further object is to provide an improved manner of forming a base with lead-in wires sealed therein f Astill further object is to provide an improved method of attaching a metal frame rto a glass plate by a molding operation.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While the invention will be described herein as embodied in certain specic forms of devices it will be understood that this is done merely for explanatory purposes and not by way of limitation. Accordingly in the drawings- Fig. 1 is a diagrammatic view to explain the method of forming a window or' screen for a cathode ray tube.

Fig. 2 is a perspective view of the metal frame member used in forming the window or screen oi Fig. 1.

Fig. 3 is a perspective view partly in section, of a ca/thode ray tube screen produced in accordance with the invention.

Fig. 4 is a schematic sectional view of a cathode ray tube envelope in which the screen of Fig. 3 is incorporated.

` Fig. 5 is a view to explain the method of forming a base or header for electron discharge tubes such as radio tubes or the like.

Fig. 6 is a sectional-perspective view of a base or header produced in accordance with Fig, 5.

Fig. '7 is a view to explain the method of form-v ing a composite metal-glass header for -radio tubes and the like.

Fig. 8 is a sectional-perspective view of a base or header produced in accordance with Fig. 7.

Fig. 9 is a vertical sectional view showing the invention embodied in a radio tube 'of the glassbulb type. 5

Fig. 10 is a bottom plan view of Fig. 9.

Fig. 11 is a vertical sectional view showing the invention embodied in a radio tube of the metalbulb type. i'

Fig. 12 is a bottom plan view of Fig. 11. 10

While various methods' of forming composite metal-glass articles with a vacuum-tight bond, have heretofore been proposed, so far as I am aware no one has disclosed a practical economical method of forming such a bond between a 15 glass or vitreous sheet and a surrounding relatively massive metal frame. `While it may be possible to unite the metal traine integrally around the edges of a glass body, by using ordinary methods, I have found that the resultant 20 bond is entirely useless when the article is to be used as part of an evacuated device such for example as a highly evacuated cathode ray tube. Furthermore while ordinary methods of forming a vacuum-tight bond may be suitable for the 25 manufacture of small devices, they are impractical in the manufacture of very llarge devices such as will be described herein below. I have found that not only is it necessary to employ a metal which has the proper coeilicient of ex- 30 pansion with respect to the glass, but it is also necessary to maintain the metal above a certain minimum temperature during the bonding operation, if a vacuum-tight bond is to be achieved. This latter step is relatively easy of accomplish- 35 ment with small parts such as the bonding of wires in glass because it is possible with the usual methods, to merely heat the glass to render it plastic after which the plastic glass may be pressed into bonding' engagement with the Wires. 4c This method of heating and sealing the parts is of course impractical where the metal part is relatively large or massive and more especially so where it is to be bonded to the glass within a mold. I have found that it is possible to bond, 4.5v

in a' vacuum-tight manner, a relatively heavy metal frame around a glass window using a molding operation, by charging the mold with the glass in a very hot and molten condition, and subjecting the glass while in a flowable state 50 to pressure whereby it is forced outwardly against the metal frame.

Referring to Fig. 1, a description will now be given of the method of providing a glass or other vitreous plate with a surrounding metal frame 55 which is bonded thereto in a vacuum-tight manner. For purposes of explanation the frame is shown in Fig. 2 as square or rectangular and it is preferably provided with a curved flange I 5 united to or formed integrally with a ilat rim 2. Preferably rthe flange I is of a metal having the same or similar coeilicient of expansion as the glass to which it is to be bonded. Assuming for example that the glass window is to consist of glass soldommercially by the designation Corning '105 AJ, then the'metal flange I may be of Kovar consisting approximately of 54 percent iron, 28 percent nickel and 18 percent cobalt, although other similar metal such for exglass may be employed.

The metal frame is positioned in a two-part mold represented schematically in section in Fig. 1 and comprising a base 3 with a rectangular molding cavity 4 corresponding in shape and size to the metal frame. The mold base 4 is also provided with a flat rim 5, a curved rim 6, and another curved rim 'I. Preferably the curvature of rim 6 is the same as that of flange I. The metal frame is seated on the mold as shown in Fig. 1 so that the flange I extends into the mold cavity beyond the rim 6. A suitable pressure ring 8 is provided to hold the metal frame rigidly in position during the molding operation. A pressure plunger 9 is provided to exert molding pressure on the glass vcharge within the mold. In accordance with the present invention the glass charge is placed in the mold in a high temperature molten condition, in the form of a hot molten mass or gathen The glass charge is heated outside the mold to as high a temperature as is practical without destroying the desired characteristics of the glass and preferably Ito an incandescent temperature. When thev hot 40 molten glass is placed Within theA mold, it retains its fluid-like condition fora short period and the plunger 8 is moved downwardly causing the molten glass to flow outwardly until the ange I is embedded therein. I have foundvthat 45 by using a relatively large mass of molten glass, which is charged into the mold at a very high temperature, it is possible to flow the glass under pressure sufficiently fast that the `flowing glass when it engages the vflange I, raises the tem- 50 perature of the latter to that necessary to effect a vacuum-tight bond with the glass when the latter hardens. I have also i'oundr that to achieve this result the glass should preferably be charged into the mold at such a temperature that when 55 it flows around the flange I, it raises the latter to a temperature of the order of 500 degrees centigrade. It will be understood of course rthat the metal frame preferably has been previously oxidized in any suitable manner. While Ido not 60 desire to be limited to any particular theory as to the formation of the vacuum-tight bond between the glass plate and the metal frame, probably the glass when it engages the metal raises it to a sufficiently high temperature at which 65 the oxide of the metal dissolves in the molten glass. It will also be understood that the mold faces are of a material having such heat conductivity and mass that the molten glass does not adhere thereto.

While a metal frame member such as described may be used in a wide variety of devices it is particularly well-suited as the window or screen of a cathode ray tube. Thus as shown in Fig. 4 the window is hermetically fastened to a tapered I 75 metal tube I I which at its constricted end may be ample as Allegheny #55 alloy and Corning G'r12 sealed to a short length I2 of Kovar or similar metal and to which the glass stemV tube I3 mayi be sealed. By employing the above-described process in. vmaking the window, it is possible to provide a substantially iiat viewing end to the cathode ray tube, and it is also possible to apply the usual fluorescent coating to the inner surface ofthe window and to treat it, prior to sealing the window to the tube. It is also possible to manufacture a cathode ray tube in which the main length II is of metal while providing a vacuumtlght seal to the window portion.

'I'he method of molding according to theinvention is not limited to the manufacture of a screen for cathode ray tubes and the broad principle may be applied to the manufacture of bases or headers for radio tubes, electric lamps and similar devices. Thus there is shown in Fig. 5 a mold that may be used in the manufacture of a disc-like base or header for a radio tube or lamp. The .mold comprises a base I4 having a circular molding cavity I5, the bottom of the cavity being provided with a plurality of small V-shaped recesses I6 terminating in elongated narrow recesses I1. Preferably the rim of the base is curved as indicated by numeral I8 for purposes to ,be described. The upper molding member is likewise provided with a plurality of small V- shaped recesses 28 terminating in elongated narrow recesses 2 I, the recesses 20, 2| being in alignment with the corresponding recesses I6, I'I. If

desired, the member I8 may be provided with a downwardly depending edge 22 which co-operates with the curved rim I8 for the purpose of forming the skirt on the base. The manner of using the moldv of Fig. 5 to form the base is substantially the same as that already described in connect.' i with Fig. 1. Prior to charging the mold with e molten glass, short lengths of lead-in wire 23 are positioned in the recesses I1 and then the mass of molten glass 25 is placed in the mold. Thereupon the member I9 is pressed downwardly causing the molten glass to ilow around the lead-in wires which become embedded therein. Because of the high temperature of the glass the lead-in wires are brought to the proper temperature to form a vacuum-tight bond. The resultant product is shown in partial section in Fig. 6 and consists of a disc-like portion 26 having an integral depending flange or skirt 21 to which the usual tube envelope may be sealed as is well-known in the radio tube art.

In certain kinds of radio tubes, it may be desirable to provide a metal wall for the enclosing envelope and the process described above is very well-suited to the formation of such a tube. Thus as shown in Fig. '7 the mold is in general the same as that of Fig. 5 except that in Fig. '7 the skirt forming portion is omitted. Instead of the header being provided with a glass skirt a metal skirt is provided. The upper and lower mold members 28, 28 are provided with circular mold cavities and with recesses 38, 3| to receive the lead-in wires 35. The `central .part of the lower mold is provided with an annular cylindrical recess 32 defining an upwardly projecting member 32a for molding the exhaust tube stem 38. In using the mold the metal cup-shaped member 33 is seated on the mold member 28 as shown, it being understood that the bottom of member 33 is provided with a circular cut-out 33h as shown. The lead-in wires 35 are positioned in the recesses 3| and a gather 34 of molten glass is placed in the mold whereupon the member 28 is moved downwardly under pressure to embed the lead-in wires 35 and the member 33 is customary in the usual press type of radio in the glass. Here again the molding pressure is -tube wherein the exhaust tubulation is formed inexerted immediately after the gather" 34 is tegrally with the press this blowing out of memplaced in the mold so that the molding pressure ber 38 taking place prior t0 Sealing the header t0 5 causes the molten glass to iiow outwardly to the the envelope. Likewise if desired, the member o member 33 which is thereby raised to the proper 32a may cooperate with a corresponding recess temperature to eilect a vacuum-tight seal. The (nOt Shown) in the Upper mOldihg member t0 product resulting from the molding operation is provide an unobstructed passage through the tu-v shown in partial section in Fig. 8. This vfigure ybulation 36. also shows the metal skirt 33a hermetically sealed This. application is a division ofl application as by welding and brazing to a tubular metal en- Serial No. 82,742, led June 1, 1936. closing member 31, itbeing understood of course What I claim is: that prior to assembling the envelope 3`|A on vthe 1. A television cathode-ray tube of the permaheader the usual electrode assembly is mounted nently sealed-Off evacuated type including a funon the header. While the drawing shows only nel-shaped metal body portion and a glass wintwo lead-in wires it will be understood that; a, dow therefor, which glass is not directly sealable greater number may be sealed into the header in a vacuum-tighty manner to the metal or said depending upon the number of electrodes to beA body portion, said WhdOW being in the fOrm 0f 8 used and the number of supports required from molded flat glass plate of a thickness to withstand the header. It will be understood of course that the pressure of the outside air over substantially the metallenclosing envelope 31 may, if desired, its entire Surface, a frame fOr Said .WiHdW 0f e constitute one of the electrodes'of theA nnished metal different from that O f Said funnel-Shaped tube. portion and scalable directly into said glass in a Figs. 9 and 10 show the header of Fig. 6 sealed vacuum-tight manner, said frame havingits in- 5 into a glass bulb containing any typical electrode nel marginal periphery Sealed irltO and arOUnd assembly or mount, Fig. 10 being a bottom plan the edge of said glass plate and its outer marginal view of Fig. 9. Likewise Figs. 11 and 12 show the periphery Sealed t0 the periphery 0f Said fuhrlelheader of Fig. 8 sealed into a metal bulb or enve- Shaped bOdy portenlope, Fig. 12 being a bottom plan view of Fig. .11. 2. A television tube according to claim 1 in Wires 40, 4| correspond to wires 23, 24 (Fig. 6).v which the said funnel-shaped body portion is sub- The remaining wires 42, 43, 44 are similarly sealed stantially rectangular in shape `at its larger end into the header. Wires 40, 4| may be connected and with rounded corners, and said window and respectively to the plate siderod 45 land the cathframe are also substantially rectangular in shape ode sleeve.l Likewise the wires 42, 43 may be conand with rounded corners corresponding to said 25 nected respectively to the ends of the cathodelarger end of said body portion.

v3. A television cathode-ray tube of the permanently sealed-olf evacuated type including a funnel-shapedmetal body portion the larger end of which has an integral radially extending iiat heater, and the wire 44'may be connected to the grid side rod 46. The wires to 44 therefore may serve as the usual contact prongs for the tube as well as supports for the various electrodes.

40 The elements of Figs. 11 and 12 are similarlyv connected to the respective wires 50 to 54 and i'urther description thereof is not believed necessary. While certain specific embodiments have been being of flattened glass of athickness to with- .stand the pressure of the outside air over substantially its entire surface, a-metal frame having disclosed herein, it will be understood that various an inwardly extending angelsealed into and 45 changes and modiiications may be'made therein .around the edge of said window in a vacuumwithut departing from the spirit and scope of tight manner, and an outwardly extending ilat theinvention. 'I'hus the tubulation stem 36 may -1 flange in a plane substantially parallel tothe window, the iiat flange on said frame being integrally be used directly for evacuating the tube or if de-- y l sired an additional length of exhaust tubing may be sealed to tubulation 36-for this purpose, it being understood that during the usual heat treatment of the tube the portion 38 being relatively thin may be melted and perforated by blowing as united in a vacuum-tight manner to the cortei spending iiat flange of said funnel-shaped portion.' I l VICTOR H. FRAENCKEL.

ange, a window for said larger end, said.window 

